Congestive heart failure remains one of the major causes of mortality and morbidity in the general population and is growing in magnitude. It affects more than 2 million Americans and consumes several billion dollars in hospitalization. Numerous well-controlled randomized trials have shown that, in many cases, vasodilator therapy has not only improved the quality of life in these patients but has prolonged their survival as well. Nevertheless, a sizeable subset of patients in chronic heart failure do not respond to pharmacologic therapy. Furthermore, while cardiac transplantation has developed into an effective treatment modality for end-stage cardiac failure, its wide application has been limited by the inadequate supply of donor hearts. Therefore, effective therapy which improves the quality of life of these patients while simultaneously increasing their longevity remains a major challenge.
It is known in the art how to provide cardiac assistance by positioning a cardiac assist device such as a pump or balloon into the descending thoracic aorta of a patient and causing the device to inflate and deflate in accordance with the natural rhythm of the patient's heart. The device is made to inflate during diastole and deflate during systole. This reduces the load on the heart and raises aortic pressure to increase blood pressure overall and more especially to the coronary arteries. Furthermore, the stroke of the device operates under various types of conditions and pressures corresponding to the changing arterial pressure of the patient. It is desirable that the device inflates and deflates at its intended rate synchronized to the patient's heart.
In addition, it is desirable to prevent the overinflation of the device. It is desirable that the device be constructed of biocompatible materials and include sufficient safeguards to insure the intended operation under circumstances corresponding to the expected range of operation for the device.